A scroll type compressor is provided with a fixed scroll and a rotating scroll, each having a volute-like scroll wall. And the rotating scroll is caused to perform revolving turning motions with respect to the fixed scroll and the volume of a compression chamber formed between the two scroll walls is reduced, whereby the compression of a fluid in the compression chamber is performed.
As shown in FIG. 6, in such a compressor 1, a cooling medium sucked from a suction port into a housing 2 is conducted into a compression chamber formed between a rotating scroll 3B and a fixed scroll 3A. The cooling medium in the compression chamber is compressed by the revolution of the rotating scroll 3B with respect to the fixed scroll 3A and is discharged from a discharge port formed in the housing 2 to the outside.
Here, the rotating scroll 3B is supported by a boss 4a provided so as to be offset from the rotation center of a main shaft 4 by a prescribed size. As a result of this, the rotating scroll 3B is supported rotatably (i.e., in a revolvable way) via a bearing 5 with respect to the main shaft 4 which is rotatably driven from the outside. In order to prevent the rotating scroll 3B from rotating on its own axis while revolving, an Oldham's ring which is not shown in the figure is interposed between the rotating scroll 3B and the main shaft 4.
Besides, the main shaft 4 is provided with a balancer 6 in order to eliminate the imbalance due to the rotating scroll 3B which has become eccentric with respect to the main shaft 4. The balancer 6 is such that a weight portion 6b is integrally formed in an outer circumferential portion of a fan-like plate portion 6a which extends in a direction opposite to the direction in which the rotating scroll 3B has become eccentric.
Although the fixed scroll 3A and the rotating scroll 3B are formed each with accuracies within prescribed tolerances, delicate dimensional errors within the tolerances nevertheless exist. Also, the accuracy and the like of the main shaft 4 have an effect on the positional accuracy of the rotating scroll 3B with respect to the fixed scroll 3A.
The rotating scroll 3B is constructed so as to be movable with respect to the main shaft 4 within a given range so that there is no harm in the relative rotation between the fixed scroll 3A and the rotating scroll 3B even if these dimensional errors exist (refer to Patent Document 1, for example). Specifically, the construction is such that the rotating scroll 3B and the balancer 6 are allowed to rotate at a given angle with respect to the boss 4a of the main shaft 4 around the center axis of the boss 4a. A stopper pin 7 is provided in the plate portion 6a of the balancer 6. In the main shaft 4, a concave portion 8 which houses the stopper pin 7 is formed in a position opposed to the stopper pin 7. The inside diameter of the concave portion 8 is formed larger than the outside diameter of the stopper pin 7 by a given size, whereby a clearance is formed between the stopper pin 7 and the concave portion 8. Therefore, the stopper pin 7 provided in the balancer 6 is adapted to be movable in the interior of the concave portion 8 around the center of the boss 4a within the range of the above-described clearance. As a result of this, when the rotating scroll 3B and the balancer 6 rotates around the boss 4a of the main shaft 4, the rotating scroll 3B and the balancer 6 are allowed to revolve in the range of the clearance between the stopper pin 7 and the concave portion 8. In this manner, the rotating scroll 3B is caused to be movable within a given permissible range, whereby manufacturing errors and the like of each part are compensated and the rotating scroll 3B is constantly brought into close contact with the fixed scroll 3A.
As described above, in a construction in which the rotating scroll 3B is movable with respect to the fixed scroll 3A, during the operation of the compressor 1, the rotating scroll 3B is pressed against the fixed scroll 3A by the pressure of the compression chamber formed between the fixed scroll 3A and the rotating scroll 3B and by the centrifugal force generated in the balancer 6. However, during the stop of the compressor 1, the rotating scroll 3B is away from the fixed scroll 3A. When the compressor 1 is started from this condition, the rotating scroll 3B collides against the fixed scroll 3A and impact noises of this collision may sometimes be generated.
Therefore, there has been proposed a scroll type compressor having a construction in which the rotating scroll 3B is movable with respect to the main shaft 4 as described above, in which an elastic body is provided between the main shaft 4 and the rotating scroll 3B, whereby an impact generated by the collision between the fixed scroll 3A and the rotating scroll 3B is absorbed (refer to Patent Document 2, for example).